NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Off Center Sextant Scope Observations
From: Greg R_
Date: 2007 Nov 22, 18:22 -0800
>
> What happens to an image of a celestial body when viewed off center in
> a sextant scope? I have a bad habit of using the lower half of the
> field of view when taking lower limb observations of the sun. I
> suspect that this increases the observed altitude slightly.
>
> Greg Rudzinski
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From: Greg R_
Date: 2007 Nov 22, 18:22 -0800
I haven't
researched this in depth, but my instinct is would it really matter?
Assuming you're talking about some sort of
refraction error (through the sextant scope optics, not the atmosphere), since
you're using the sextant's mirrors to make the lower limb tangent to the horizon
wouldn't both be refracted by pretty much the same amount if viewed at that
point (or really any point) of the scope?
But you can probably answer you own question -
how close do your observations come to a known GPS position for the same
location? If you can get to within a mile or so consistently from a shore
location (no matter what part of the scope you use for the sight) I'd say not to
worry about it. :-)
--
GregR
----- Original Message -----
From: "Greg Rudzinski" <gregrudzinski@yahoo.com>
To: "NavList" <NavList@fer3.com>
Sent: Thursday, November 22, 2007 4:39
PM
Subject: [NavList 4015] Off Center Sextant Scope
Observations
> What happens to an image of a celestial body when viewed off center in
> a sextant scope? I have a bad habit of using the lower half of the
> field of view when taking lower limb observations of the sun. I
> suspect that this increases the observed altitude slightly.
>
> Greg Rudzinski
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To post to this group, send email to NavList@fer3.com
To , send email to NavList-@fer3.com
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